DESCRIPTION (Adapted from applicant's description): With previous interest and experience in understanding cell identity, the candidate is proposing an 5-year mentored research experience to the mechanisms of human development using genetic studies in the fruit fly, Drosophila melanogaster. Embryos mutant for the Drosophila naked (nkd) gene demonstrate early mis-expression of the key secreted patterning molecules Wingless (Wg) and Hedgehog (Hh), and subsequently mispatterned ventral cuticle, implicating the nkd gene in the specification of cell identity. Previous experiments have suggested that nkd antagonizes signaling by the Wg protein, homolog of the vertebrate proto-oncogene Wnt-1. The nkd gene encodes a novel protein with a putative Ca2+ binding EF hand motif. Genetic mosaic analysis and misexpression assays will be used to demonstrate whether nkd is required in Wg-producing cells, receiving cells, or both. Monitoring of Nkd protein and mRNA levels by confocal microscopy, both in wild type and in various mutant backgrounds, will be used to understand how nkd regulates wg function, and vice versa. The ability of Nkd to bind Ca2+ will be tested. To understand how Nkd functions in signal transduction, the yeast two hybird system will be used to isolate Nkd-interacting proteins. Finally, to understand the functional domains of the Nkd protein, as well as to serve as a probe for learning how vertebrate Wnt proteins function, nkd vertebrate homologs will be isolated by low stringency and PCR-based techniques.